When I was running a TDDFT calculation for NH3 molecule with the following input geometry:
geometry
N 0.0000 0.0000 0.0000
H 0.0000 -0.9377 -0.3816
H 0.8121 0.4689 -0.3816
H -0.8121 0.4689 -0.3816
end
The job failed with the error information "tddft_init: non-Abelian symmetry not permitted".
The point group of NH3 is C3v which is indeed not Abelian. The corresponding Abelian subgroup is Cs. So I added this symmetry in the input file like this:
geometry
N 0.0000 0.0000 0.0000
H 0.0000 -0.9377 -0.3816
H 0.8121 0.4689 -0.3816
H -0.8121 0.4689 -0.3816
symmetry cs
end
However, in the output file the program added three hydrogen atoms and it became a strange geometry:
Geometry "geometry" -> ""
-------------------------
Output coordinates in angstroms (scale by 1.889725989 to convert to a.u.)
No. Tag Charge X Y Z
---- ---------------- ---------- -------------- -------------- --------------
1 N 7.0000 0.00000000 -0.00001538 0.00000000
2 H 1.0000 0.00000000 -0.93771538 -0.38160000
3 H 1.0000 0.00000000 -0.93771538 0.38160000
4 H 1.0000 0.81210000 0.46888462 -0.38160000
5 H 1.0000 0.81210000 0.46888462 0.38160000
6 H 1.0000 -0.81210000 0.46888462 -0.38160000
7 H 1.0000 -0.81210000 0.46888462 0.38160000
This is definitely not correct. Only the atom 1, 2, 4 and 6 are in the input file. I have the same problem for the CH4 molecule (in which 4 hydrogen atoms were added).
I also tried the Z-matrix using the variables that make it completely symmetric. But there is still the same error.
Now the only way that I can run this job for this molecule is to completely turn off the symmetry. But this makes it very difficult to analyze the result since it is impossible to identify the states based on symmetry.
I don't understand why the program automatically added several hydrogen atoms. Is there any solutions for this kind of problem?
Thanks very much.
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